The invention generally relates to a downhole electrical-to-hydraulic conversion module for well completions.
For purposes of producing well fluid from a well, a tubular member called a production string typically is run into the well bore. The well bore typically extends through several production zones, and the production from each zone may be controlled for purposes of manipulating downhole pressure, controlling water production, etc. In intelligent completions, hydraulically-controlled valves may be placed in the production string for purposes of controlling production from the zones.
As a more specific example, a typical hydraulic valve may be operated using two control lines. Each control line communicates a control pressure to one side of a piston, which opens or closes the valve member. The dual line valve, however, may create challenges regarding the number of control lines that are run into the wellbore. More specifically, there are often limitations on the number of control lines that may be run into the well, as a result of the limitation on the number of control line penetrations at the wellhead, tubing hanger and in some cases the production packers.
One approach to limit the number of control lines that are run into the well involves the use of single control line valves. A single control line valve typically relies on a stored energy charge downhole, such as a nitrogen spring or a mechanical spring that works in conjunction with either the annular or tubing pressure. However, because downhole conditions may change over time, the selection of the spring and/or nitrogen charge may limit the overall operational envelope of the valve.
Another approach to limit the number of control lines involves using a hydraulic multiplexing scheme. However, this approach typically requires a relatively complex scheme of valving to allow pressures at different levels to address the downhole valves.
In another approach, a common return control line may be used for simple two position (i.e., open and closed) type valves, but operation may be challenging as the state of each valve must be first determined in order to derive the sequence that must be applied to operate the valves.
Thus, there is a continuing need for better ways to control downhole tools, such as valves, for example.